Venturi pumps are useful devices that are utilized in a myriad of situations and applications. For example, venturi pumps are used in industrial applications and on construction sites to pump an assortment of fluids. In home applications, venturi pumps are used to drain pools, fountains, ponds, aquariums, sinks and in innumerable other applications.
Venturi pumps make use of a venturi to pump fluids from one area to another. In general, a venturi is a short tube having a tapering constriction (or throat) at or near the middle of the tube. This constriction causes the velocity of the fluid at the throat to increase and a corresponding decrease in fluid pressure. The low-pressure area created at the throat is particularly useful in measuring fluid flow and for creating a suction force. This suction force is used in many applications, such as for driving aircraft instruments and for drawing fuel into the flow stream of a carburetor.
One type of venturi pump that makes use of a venturi to create a suction force and draw fluid into the pump is discussed in U.S. Pat. No. 4,963,073 by Tash et al. entitled, “Water Pressure Operated Water Pump”. Disclosed therein is a convenient, easy-to-use and inexpensive pump for pumping water. The device uses water pressure from a standard garden hose connection as the power to pump the water. The device has a primary inlet, a secondary inlet, and an outlet nozzle. The primary inlet is for inputting liquid (such as water from a garden hose tap) at a high velocity through a venturi. This high-velocity flow creates a low-pressure area at the throat and generates the motive power necessary to drive the pump. The secondary inlet is positioned at the throat and opens into the venturi at the throat. The fluid being pumped is drawn into the venturi through the secondary inlet. The output nozzle is for outputting the fluid combination from the primary and secondary inlets.
When the water from the garden hose tap flows under pressure into the primary inlet, the velocity of the water is greatly increased by a venturi that is positioned in the pumping chamber. The increased velocity of the water through the venturi causes a corresponding drop in pressure. This drop in pressure causes the pressure in the pumping chamber to be less than the pressure of the fluid to be pumped. This causes the fluid being pumped to be drawn through the secondary inlet into the pumping chamber and be ejected through the outlet nozzle.
In existing venturi pumps, the cross-sectional areas of the primary inlet, secondary inlet, throat, and outlet nozzle are fixed. This means that the inlet-to-throat area ratio and the throat-to-outlet nozzle area ratio are fixed. This leads to at least three problems with existing venturi pumps.
First, when a column of fluid (or head) at the outlet nozzle is high enough, the pump will be unable to pump the fluid any higher. This is because the motive force pumping the fluid through the outlet nozzle is in equilibrium with the weight of the fluid head at the outlet nozzle. A second problem with conventional venturi pumps is that if debris or other contaminants (such as leaves or rocks) block the secondary inlet the flow rate decreases and the pump performance suffers. In addition, viscous fluid (such as oil or a combination of water and mud) requires greater suction in the pumping chamber than a less viscous fluid (such as water). A third problem is that a rigid foreign object in the fluid being pumped (such as a rock) may be sucked through the secondary inlet and lodge in the outlet nozzle. In extreme situations, the foreign object may completely block the outlet nozzle, thereby effectively shutting down the pump. Therefore, what is needed is an improved venturi pump that overcomes the aforementioned problems to provide increased performance and usefulness without undue cost and complexity.